(a) Field of the Invention
The present invention relates to a power supply, a backlight apparatus, and a display device.
(b) Description of Related Art
Display devices used for computer monitors and television sets include self-emitting displays such as light emitting diodes (LEDs), electroluminescence (EL) displays, vacuum fluorescent displays (VFDs), field emission displays (FEDs), and plasma display panels (PDPs), and non-emitting displays such as liquid crystal displays (LCDs) that include a light source.
An LCD includes two panels provided with field-generating electrodes and a dielectric anisotropy liquid crystal (LC) layer interposed therebetween. The field-generating electrodes supplied with electric voltages generate an electric field in the liquid crystal layer, and the transmittance of light passing through the panels varies depending on the strength of the applied field, which can be controlled by the applied voltages. Accordingly, desired images are obtained by adjusting the applied voltages.
The light may be emitted from a light source equipped in the LCD or may be natural light.
A lighting device for an LCD, i.e., a backlight assembly, usually includes a plurality of fluorescent lamps such as external electrode fluorescent lamps (EEFLs) and cold cathode fluorescent lamps (CCFLs), or a plurality of light emitting diodes (LEDs) as light sources, which uniformly transmit the light to an entire front surface of the LC panels from a rear of the LC panels.
When using the fluorescent lamps, characteristics of pixel elements of the display device deteriorate due to power consumption and heating by the fluorescent lamps.
In addition, the fluorescent lamps are elongated in the shape of a stick, which can easily break on impact. Moreover, the luminance of fluorescent lamps can vary with temperature or position the luminance of the image quality can vary.
However, when using the LEDs, since each LED is a semiconductor device, the lifetime of the LED is longer, the speed of the LED is faster, and power consumption is lower than the fluorescent lamps. The LED is also sturdy and miniaturization thereof is easy.
LEDs can be used as light sources in computer monitors and in middle or large sized LCD television sets, as well as light sources for small sized LCD displays, such as in a mobile telephone or a light source.
Fluorescent lamps are activated by an AC (alternate current) voltage, while the LEDs are activated by a DC (direct current) voltage. Accordingly, for systems using the LEDs, the backlight assembly includes a power supply converting an AC voltage into a DC voltage and changing a magnitude of the DC voltage into a predetermined magnitude.
Driving voltages applied from the power supply are converted into voltages with a square wave for driving the LEDs. However, if the level of the voltage is changed, and/or if there are excessive noise levels, an excessive amount of current exceeding specified instantaneous maximum values can flow to the LEDs, and the LEDs may be destroyed.
Therefore, a need exists for a system and method for a power supply, a backlight apparatus, and a display device.